CARBONIFEROUS LIMESTONE. II7 



could not discover organic structure. The limestone of Portage 

 River makes an excellent white lime ; its composition is, 



Carbonate of lime 96.9 



" magnesia i.o 



Alumina and iron 0.7 



Insoluble residue. 1.4 



99-0- 



North of Portage River, along the eastern margins of the central 

 coal field, no outcrops of the carboniferous limestone are known. 

 South of Saginaw district, through borings made along this line, or 

 more toward the centre of the peninsula, the carboniferous lime- 

 stone series is found very poorly represented, and frequently seems 

 to be altogether missing. 



At Lansing, many deep borings have been sunk, one to a depth 

 of 1400 feet, and one in the yard of the Lansing Hotel to a depth 

 of 740 feet, of neither of which was I able to get a record. Another 

 well in the State Reform School, having a depth of 506 feet, was 

 carefully recorded ; but the identification of rocks by comminuted, 

 sand-like particles, as they are brought up by the sand pumps, is 

 so difficult that one can rarely get from the well-borers, who gene- 

 rally keep such records, names appropriate to the various forma- 

 tions encountered. Contemplating such a record, with the intent to 

 form an idea of the exact uature of the superimposed rock series, 

 one is often disposed to give up in despair, if he is over-scrupulous 

 to give rein to his imagination, or to arrange things to suit his own 

 notions. The register of the boring at the Reform School reads as 

 follows : 



Drift (alternations of clay, sand, gravel and 



boulders) loi ft. 



Soft sand rock 3 " 



Hard fire-clay 4 " 



Soft, white sand rock 13 " 



Soft, sandy fire-clay 15 '' 



Hard sand rock 119" 



Hard, fire-clay, alternating with beds of sand 



rock variable in color from whitish to blue. 64 " 

 Cherty lime i " 



